PURPOSE OF REVIEW: To review the most used tests for diagnosis of pulmonary hypoplasia, and their pertinence in different pathological conditions. RECENT FINDINGS: The two-dimensional biometric parameters are not accurate enough to be applied in clinical practice, except for the lung-to-head ratio (LHR): the observed/expected LHR remains the best predictor of pulmonary hypoplasia in fetuses with congenital diaphragmatic hernia. The introduction of three-dimensional ultrasound tecniques has allowed to directly measure lung volume. Three-dimensional-derived nomograms seem reliable for the prediction of both normal and pathological pulmonary volumes. MRI is attracting increasing attention. The studies recently published on this method are highly heterogeneous; universally accepted standardized values for the prediction of pulmonary hypoplasia are, hence, not available. Finally, some authors proposed Doppler ultrasound velocimetry to detect changes in pulmonary vascularization that correlate to pulmonary hypoplasia. However, a well-defined test to predict pulmonary hypoplasia has not emerged so far. SUMMARY: The prediction of the lethal type of pulmonary hypoplasia is pivotal to improve counseling and neonatal assistance. There is not a single test that can, at least for now, predict postnatal lung function. For different underlying pathologies, different combinations of clinical, ultrasound, and MRI parameters seem to better assess the risk of pulmonary hypoplasia.